On Sonorous Vllratlons. 235 



more intimate action. Every kind of friction produces not 

 only heat, but electricity also. De la Place, and Biot, have 

 already attracted the attention of philosophers to the first of 

 these pha^noniena ; I am of opinion that the latter of them 

 i'ctjuires much more attention. I alwavs found iu my ex- 

 periments that sand, or dust, adheres much more to those 

 parts to which the movement of the sonorous bodies had 

 fixed it, than it did to the other parts. 1 have often thrown 

 fiCsh sand over a plate of glass, upon which I had already 

 produced a figure. I shook it gently after having reversed it, 

 and I always remarked that the saud which formed the 

 figure renjained adhering, while the other part detached it- 

 self. The adherence of erains finer than ihose of sand is 

 very remarkable. I also discovered, with the assistance of 

 Coulomb's electrometer, indications of electricity in those 

 [ilates which had emitted a sound; but I have not repeated 

 these experiuMnts sufficiently to enable me to detail them. 

 T discovered on the above occasion, that the edges and 

 angles of bodies act upon Coulomb's electrometer almost 

 always ; and I propose to myself a new course of experi- 

 ments upon this subject. The celebrated Kittcr, to whom 

 I had comnumicatcd my experiments upon the part which 

 electricity acts in the phsenoniena of sound, had' long ago 

 discovered that the electrical pile of \'olta is capable of pro- 

 ducing sound, when a shock is received frou) it in the ears. 

 In a work about to appear under the title of " A System of 

 Klectrical Bodies," lliis great philosopher makes it clear 

 tiiat a body acquires positive electricity by compression, and 

 negative bv dilatation. Thus we may say, that there are in 

 each sound as many alternatives of electricity, positive and 

 negative, as there are oscillations j but the union of two elec- 

 tricities produces a commotion : thus there are in one 

 sound as many extremely weak electrical commotions as 

 tiiere are oscillations. Each of these insulated commotions 

 would be absolutely insensible ; but when received in a 

 very great number, in a period too small to distinguish the 

 one from the other, they always produce a sensible effect, 

 fipecially since positive electricity renders the organ more 

 sensible for the negative than it was before, and vice versa. 



The 



